FIG. 10 is a sectional view showing a configuration of a conventional circuit board 1. Circuit board 1 includes heat-dissipating plate 2, wiring board 5 disposed on heat-dissipating plate 2 and having resist layer 3 and resin layer 4, and heat generating component 6 mounted on wiring board 5. Resist layer 3 is provided on a surface facing heat-dissipating plate 2 in wiring board 5. Heat-dissipating plate 2 is formed of metal having high heat-dissipation property.
Furthermore, heat transfer portion 7 is provided in a part of resin layer 4 of wiring board 5 facing heat generating component 6. Heat transfer portion 7 is formed of metal having excellent heat transfer characteristics, and transmits heat generated by heat generating component 6 to heat-dissipating plate 2. Resist layer 3 electrically insulates heat transfer portion 7 from heat-dissipating plate 2.